Both players were involved in an angry exchange after trading shots at the net in the 12th game of a tense fifth set after Kiefer threw his racket as Grosjean was playing.

The Frenchman missed an easy volley and the point was awarded to Kiefer. Grosjean protested bitterly to chair umpire Carlos Bernardes and match referee Mike Morrissey but the point stood.

Twenty-first seed Kiefer, who complained often about line calls and was earlier handed a code violation for swearing, broke a tiring Grosjean's serve in the 14th game of the set to close it out after four hours and 48 minutes, the longest match of the tournament.

He will play either top seed Roger Federer or fifth seed Nikolay Davydenko in the semi-finals.